Light-Load Efficiency Optimization Method

A method of maintaining high power-conversion efficiency across the entire load range and its circuit implementations are described. The proposed method substantially increases the conversion efficiency at light loads by minimizing switching and driving losses of semiconductor switches, as well as core losses of magnetic components. These losses are minimized by periodically turning off and on the power converter and by controlling the converter so that when the converter is on it operates at the power level that exhibits the maximum efficiency. The performance of the proposed method was evaluated on a 500-W, 400-V/12-V dc/dc converter and a 1-kW ac/dc boost PFC front end.